Stereoscopic position indicating means



R. H. RANGER 2,4?7,65i

STEREOSCOPIC POSITION INDICATING MEANS Filed June 27, 1944 4 She ets-Sheet 1 a! VALN TOR AITO EV 1949. R. H. RANGER 2,477,651

STEREOSCOPIC POSITION INDICATING MEANS Filed June 27, 1944 4 Sheets-Sheet 2 JZ STEREOSCOP/C DES/6W FOR LEFT INDICATOR M R/CHARD M RANGER ,4 7T OBIVE Y Aug. 2, 1949. R. H. RANGER 2,477,651

STEREOSGOPIC POSITION INDICATI NG MEANS Filed June 27, 1944 4 Sheets-Shee 3 JZ STEREOSCOP/C DES/6N FOR RIGHT INDICATOR 3 m RICHARD H. RA NGEH A TTORNEY Aug. 2, 1949. R. H. RANGER 2,477,651

STEREOSCQPIC POSITION INDICATING MEANS Filed June 27, 1944 4 Sheets-Sheet 4 3 Figure 1 is a schematic diagram of a radio 10- cating system embodying the invention.

Figure 2 is a view showing the manner in which a map is marked for use in the system for the left eye. (In use, this view is printed on a transparency and the ,reverseof the map is presented to the'mirror to bring the image into correct orientation, as the mirror again reverses the image to make it right.)

Figure 3 is a view showing the manner of marking the map for the right eye.

Figure 4 is a view showing the stereoscopic ef fect produced by the images of the marked maps.

Figure 5 is a view showing a cross section cutaway of the apparent stereoscopic image.

Figure 6 is a view of the screen of an oscilloscope used in a plan position indicator.

Figures 7, 8 and 9 are diagrams explanatory of the method employed.

The drawings indicate the echoes by black marks, whereas the normal plan position indicator gives them actually as bright white spots. As a matter of fact this invention works better by reversing the beam modulation control to get dark spots along bright traces to indicate echoes. This bright trace illuminates the transparencies excellently, and the echoes show up as black dots against the transparencies.

The radio locator system comprises a high frequency pulse transmitter and receiver 45 producing pulses which emanate from an antenna 46 and are propagated by a reflector 41. The transmitter and receiver 45 is pivotally mounted on a post 48 for rotary movements in a vertical plane. The post 48 is mounted on a pedestal 59 for rotary movements in a horizontal plane. Attached to the device 45 is a segmental gear 49 in mesh with a pinion which is manually manipulated to cause rotary movements in a vertical plane.

Forming a part of the system are two plan position indicators 9 and I0, which include oscilloscopes having respectively over the faces thereof sheets II and [2 of transparent material with transparent maps thereon of the locality being January 20, 1944, and each comprises a cathode ray tube in which a cathode ray sweeps back and forth from the center to the edge of the scanning disc, and at the same time is rotated uniformly over a complete circle. The radial motion back and forth of the trace from the center to the edge of the disc is so rapid that the efiect is that of a continuous line extending from the center to the edge of the scanning disc, and this line is rotated around the disc with the center of the disc as an axis. When a pulse reflected from an object located is received by the radar device, this pulse appears upon the luminescent scanning disc of the plan position indicator. The distance of the pulse from the cen- 'ter of the disc indicates the range of the object,

and angular position of the pulse from the base north-south line indicates the azimuth of the 'object.

3. Each map has a plurality of circular contour lines 60 marked thereon. It will be noted that map at H in the mirror I3 is viewed simultaneously with a direct view of the map at l2 a stereoscopic effect is produced, and there appears to be a plurality of concentric ridges GI and valleys 62 (see Figure 4) The spaced apart circles give the effect of a cone'rising at the center of the map. The height of this cone at the apex is 25,000 feet, and it falls in 5,000 foot levels to the ground level at a distance of approximately two miles radius from the center. The contour spacing is then continued radially outward, rising around the central cone. This ridge then falls away again in 5,000 foot levels to the ground, and then rises again to a second ridge, and so on.

In order to enable the eye to pick up the elevations readily, diagonal'lines I25 are run between the circular contour lines representing the bottom and the top elevations. Eight points on each such circle are chosen, and the lines run up and down. This helps materially in focusing the eyes.

To determine the pro er eccentricity in drawing the circles to give the stereoscopic effect, an imaginary situation has been developed. That is, in looking at any given point, the images representing that point for the left and the right eyes are assumed to be those that would be observed at distances of infinity from the map but still at an angular separation for the eyes as they would be as if they were only 15 inches from the map. This is an important point. At fifteen inches from the map, and with 2 /2 inch separation of the eyes, the angular divergence from a point on the center of the map to each of the eyes is approximately ten degrees. But this divergence is assumed to be constant and equal for any point on or above the map. This would be the hypothetical situation of having the eyes at infinity but still with this same angular divergence of ten degrees.

At first, this divergence was distributed equally for the right and left images, but when it was found equally effective to have the angle for one eye to be perpendicular to the map, and all the ten degree divergence used on the other. An arbitrary convention has been made of assuming the image for the right eye is the perpendicular projection of all points above the map, onto the map, and the image for the left eye is made up 'by projecting all points above the map at an 60.

angle of ten degrees off the vertical onto the map.

No account is taken of the fact that in normal stereoscopic effects the eye is at a nearby single point and looks forward and to the left and right. This new scheme simplifies the drawing considerably and gives much clearer delineation of the height of each portion above the map. It likewise prevents the great distortions towards the outside of the map which would otherwise occur; and simplifies the adaption of the idea to actual radar presentations.

Normal stereoscopy is really a combination of perspectiv'e in each view and then a varying angular divergence for each portion of the view. This new stereoscopy in which the angular divergence is constant for all elevations has been sateen satin stereo-parallax hecaiiseit gives stereoscopic fi ctsby'pai'allel'projections; It has' the tiec'ided'adva'iitage of giving equal displacement for air p'o'ints at equal heights above the map. It fliiks'for easier observance and much inor'edefiiiit'estimates of height.

Forthe left eye image; the center of each of the contour circles is offset to the left (when "diii the device) byaln-a'moiiiit proportional totlihight that a given circle contour is supiiosdto'r'epresent. These centers appear on the right-iii Figure 2' because this-is'afront view, sees thfoiigh mirror I3 Fignre 1 shows; of "ear of the map constituting transparent l siee'ea oa plan position indicator 9. As th ftang'ent of 10" is approximately one-sixth, it seem that the eccentricityis -one-siiith' the aeration to be represented. So, for equal heights, tfiecii'cular contour lines representing the same have centers displaced to" the right of the ground center of the map by anamount representing one-sixth of the height to be indicated. a The net effect of the circles and diagonals: is tbbiiild up a very delicate illusionary structure iiifiiie' lines above the map, looking like a jelly E615;

The presence of the map is a very distinct "ciitrihntion to the-apparent reality of the stereoe'sefi'tation; firWll-defiii'ed base from which the contur line's appear to rise. This illusion is also helped by Having other references at the various heights. Num ers and words indicating the heights are properly spaced-to appear to" be at the same apparent heights as they indicate.

It? is tobe noted that for points above the g the left projectionsare moi/ed to'th'e'l'eft screen H. They appear on the right in Figure 2 bec'ause'thisis a front view as reversed-by mir 1 "for" it? This is t'omake-- points nearer: the left eye diverge" to the right. So the movement to th'e l'e'f-t-on the print actually makes the left eye move to' the right to accommodate in focusing th t wo eyes on the spot.

It i's assumed that the radar is-loc'ated at the "center of this whole presentation and on the groundlevel. The normal trace "will then radiate out from this center. (See Figure 6); If the radar pointed horizontally straight out, the trace should appear as being at Zer-oelevation throughoutitslength. This would obviously he the iidriiial presentatiomas is now accomplished in plan position indicator Work. As the radar sweeps around; a Selsyn connection, accomplishes the: rotation of the position indicator controls to ca'use'thesweep to change angle to correspond tbt'lie-changing angle of the radar.

Now, assume that the radar is changed from the horizontal position or zero elevation, to some: higher position, say 10. This is accomplished by iiianually rotating apinion 99' as to cause rotation of the segmental gear 49. (See Figure 1 Startingwith the sweep running straight'out to the right in an easterly direction from the cen-' terof the map, as far as theanglesare concerned both the left and right presentations (Figurefi) will be at the same azimuth angl'efor this particular'condition. They will again be at the-same azimut angle when the sweep gets around I8D' ina weSterIy direction. At all other points the two presentations will not coincide.

G'cirisidering' the right presentation alone; inasmuch asthe radar is 'no'w directed upward at an aneieat 10 it is' obvious that'as the tracdhow' on any of the imaginary ridges'in-space The roads, towns and printing give J 6 comes sect, he'eyewin see aforep ojee on the trace (iii-the map cansthat a oteritio'meter control of the etentof th weep must he realized when the radaris i'aised elevation to this 10-"ang1e. with this-- presentation the trace-- Will be" fore shortened in direct proportion to the cosine of 1edfelyatior'i'z iiiodifi'd} l-iowvi, for the'lit eye over ill see all 1 points which 1- displaced to the right devieeispomtedatanaagh sci-rarer anc entthat the devait is obvious-thattiie sucgrit for the left eye obser- "e is era-i1y proportional to oi'xithe" center; so that one position elevation" and saw-far any point on Ii ear adjustment-on the I'riasiiiu' s are progressively to t for anyaznnuth sesinorth-south vertical line iihuth anglefor the 1eiteye 'ill 'begdeci ased back towards the essence. As a-matter of fact, instance willbe at the from east; taken, displacement centeron the I 1 "'sfii'finding t6" the heightof tfie 'filrtl'ist pbi tJontlie trace V.

In the-s t'e own-iii Figurer the operator the mirror the image of the'left indicator [1" with the left eye; and looks directly at the 'i i'glitindicaifdr Iitvithth right eye.

For tlifight-Stefbgi iii, the projection Will be'a can view oi everything above the ground reii'rese'r'i'ted asa i/ert'ica-l' projection right down tofth'e that): This is as if'the' eye were at infinity 160 fig vertically-"commune area. For the left ii'ffa tli (inethat is-ilsd' through the mirror, pi'opei"parallax to the'ri'ght must'be introduced to "'Ve the stereoscopic effect; As the mirror rev "see the: action 'tHi'Si'q'mresa Shift to the left higlit above the map.

aigets on u the appropriate azimuth i'r1'--- tria -planetsthe rh'ap; In other words, this is for zero elevation;- NOW, suppose'the radarisel votes at ai'i merea shdw'ri in Figure 7 to pick up an -air plane" abovethe-area covered by' the mapz The samereianve position would be indicated a-s 'shown bythe-planeon the line Kat h. '(0 It is obvioils that n'owthe trace on the'pla'n position indicathnshhldbe reduced to the length 9 which.is-thelength ont along K times the cosine ofahglm:

'Every p'oint on the trace which normally mp 70 resents the fuli clis'tancewlor 6=inches:must'-1ike- Wise now be reduc which reduces the i. e. y=lc ed by a potentiometer control sweep to this cosine amount, 0s a. So every point will be represented on the ground level as a vertical projection down from the point indicated above the map. The 1dotted line coming down from h to H indicates his.

For the right stereogram all points will therefore be represented as shown first on Figure 7, then on Figure 9. Figure 3 is a plan view for the right eye and Figure 2 is a plan view for the left. For any given azimuth on the right stereogram, say angle 0, the trace should be represented along the line U but its length will be foreshortened by the same amount as indicated in Figure '7, the cosine of the angle times K, or u=K cos a. This potentiometer can be mounted directly on the elevation control of the radar device.

For the left stereogram, it is necessary to use a compensating arrangement to change'the sweep in accordance with the elevation and azimuth angle as well. A mechanical linkage will accomplish this. This is shown diagramatically in Fig ure 8 and structurally in Figure 1. At t a gear is driven by a Selsyn, operated from the vertical elevation control of the radar. This gear pulls the rod Q back and forth so that the point at is at a distance corresponding to the foreshortangle of elevation zero. As the radar is raised, Q will be foreshortened by action of the Selsyn o we are workin the left stereogram this means that m over it (see iigure 7) is one-sixth, which therefore, makes ;he tangent of B equal to one-sixth; so finally, n is one-sixth of the sine of angle a as n equals une-sixth 'of the sine of angle a. Therefore, me- :hanical arrangements must be made by cams or tl'leIWiSE! to move the rotation point of arm Q to he right as the radar is pointed at higher eleations. The two arms R and Q are pivoted toether at J. For zero elevation, m is zero and :e gear t is moved back to the left, and the two enters e and d are in line with each other.

Now, assume an angle of azimuth c for both the ght stereogram and this are as shown at c. We will get a correct center Jsition of the left plan position indicator trace,

s shown as R, determined by the point e which :presents a fixed point controlling the angular on a pin 29, wh

' 23 is a shaft 25 fixed to a Dini sweep of R. It is seen that when the arm R r0- tates it engages a pinion s. This pinion drives a potentiometer control which determines the gain for the sweep of the left plan position indicator in such a manner that the actual mechanical length of R from point h to e is duplicated by the sweep of the trace on the left plan position indicator.

Finally, if the angle of rotation f is transmitted directly to the control of the left plan position indicator 9 as by gearing 34 and shaft 65, Fig. 1, We have a means of determining the exact angle at which the left position indicator trace should be to give a correct left stereogram for all points picked up on the radar and presented in parallax by the left stereogram. (It must be remembered that all of the above discussion is for apparent points, i. e. as seen in the mirror. The actual trace will be reversed left to right as well as all the movements in the plan position indicator 9.)

Any points such as h on the actual radar as indicated on K will be fcreshortened by the appropriate amount on the sweep determined by arm R of Figure 8.

A mechanical apparatus sweep of the left for controlling the plan position indicator is shown in Figure 1. The apparatus is shown greatly enlarged relative to the plan position indicator. In this apparatus, a bed plate 20 is slidably positioned between guide flanges 2|, and has, projecting up therefrom, a post 22 which rotatably supports a sleeve 23 fixed to a casing 24. Rotatably positioned in the sleeve 23 is a shaft 25 fixed to a casing 24. Rotatably positioned in the sleeve on 26 in mesh with ck are positioned in 29 is lower than the pitch line of the rack 21 by an amount equal to the radius of the pitch circle of the gear 26 so that the distance of the pivot point 28 will be uniform and equal to the displacement of the rack caused by rotation of gear 26 in casing 24. The rack 27 has one end bent back on itself at 28, and is rotatable ich is also rotatably connected to a rod 30 passing through a short tube 3| which has fixed thereto a shaft 32 rotatably supported by a post 33 and connected to a member 34 which controls the rotation of rotating magnets of the left plan position indicator for causing the sweep to rotate about the face of the cathode ray tube as above explained and illustrated in Figure 6. In Figure 1 this connection is indicated by the arm 65 with appropriate bevel gears starting with 34. It is to be noted that counter-clockwise rotation of 24 accomplishes clockwise rotation of 66 which is corrected to give the reversed image. It is likewise obvious that these bevel gears could be eliminated and member 34 could work directly on the P. P. I. magnetic rotation. It is shown this way for clarity.

Supported by the rod 30 is a variable resistance engaging a contact 36 supported by the tube a rack 27. The pinion and ra casing 24. Pivot Fixed to sleeve 23 is a gear 31, in mesh with a pinion 38 fixed to the shaft of a Selsyn motor AA. The post 22 has a slot 39 in which moves a small wheel 40 rotatably mounted on a stub shaft 4| eccentrically fixed to a gear 42 which is rotatably supported by a stationary post 43. The gear 42 is in mesh with a pinion 44 connected to the shaft of a Selsyn motor CO. The shaft 25 passes freely through gear 37 and is connected to the shaft of a Selsyn motor BB, which gear 3'1, the gear and motor rotati This apparatus is associated W1 is mounted on ng together. th a radar de- 9 vicewmch comprises a radio receiving andt'ransknitting apparatus 45 for emitting-very sl iortradio waves from an antenna-GE- and projecting them by a reflector 41.

The device ispivotally mounted on a post 48 and carries a toothed segment-49 in mesh witha pinion 50 connected to the shaft of a Selsyn mo- 1301 C. The segmentts' carries-archer 52 which movesin a slot 53 of a vertical bar 54, of a Scotch ybke theupper end ofwhich i's'slidable ina channel 55, and the lower end-is slidable on an angle bar 56 and carries a rackST in mesh with a pinion 58*e0nnected to thdshaft of a 'Selsy-n motor B. Thepost-BB is rotatably'inbu-nted on pedestal 59 and carries a gear 60 in "mesh with a piniontl connected to the shaft of a Selsyn motor A.

Selsyn motors A, B, C, are connected respective- 1y to Selsyn motors AA, BB, and CC, and Selsyn A is also connected to the azimuth Selsyn SI of the right position indicator ID, to control the rotation of the rotating magnets mentioned above. Selsyn A drives Selsyn AA with gearing to make a one to one rotation of gear 31 with azimuth rotation of the radar. B Selsyn operates Selsyn BB to give a one to one movement of rack 21 with linear movement of scotch yoke 54 assuming each moves a maximum of six inches. Selsyn C operates Selsyn CC with appropriate gearing to make it a six to one reduction, so movement of post 22 is proportional to one sixth the sine of the angle of elevation.

Terminal of the radar device is connected to one end of resistance 35, to one end of a variable resistance 13 on segment 49, and to right plan position indicator l0. Terminal H is connected to the other end of resistance 35, to the left plan position indicator 9, and to the other end of resistance '13. Contact 36 on tube 3| engaging resistance 35 is connected to left indicator 9; and a sliding contact 14 engaging resistance 13 is connected to right indicator II).

In operation, the horizontal movements of the radar device are transmitted through Selsyn A to Selsyn 5| to control the right indicator I'll. These movements are also transmitted from Selsyn A to Selsyn AA to rotate spur gear 38 and thus gear 3?, sleeve 23, casing 25, and through :bar 21, rod 38', and member 34, to affect the rotating magnets of the left indicator 9.

Vertical movements of the radar device will cause rotary movement of segment 49 to vary the position of the contact 14 on potentiometer 13 and thus afiect the applied voltage of the sweep circuit of right indicator ill.

At the same time, movement of segment 49 will rotate pinion 53 to cause Selsyn C to rotate Selsyn CC, which rotates gear 42, by spur gear 44, to cause eccentrically mounted roller 40 to move in slot 39 and move post 22. Since the post 22 is fixed to plate 20, the latter will slide in the guides 21, carrying therewith the structure mounted thereon to cause rod 30 to move in tube 3|, and moving contact 36 on the potentiometer 35 to vary the voltage applied to the sweep circuit of the left indicator 9 as above described. The object is to get a direct interpretation of the amount of motion of the bar 54 to the right on Selsyn B. The rack 21 is moved an amount proportionate the movement of bar 54. The bar 54 must move 6 inches for 90 degree vertical rotation to give a 6-inch movement to rack 21 to establish the correct procedure for the length of rack 21 to be proportional to the cosine of the angle of elevation of the radar device. In other words, the distance of pivot 29 is 6 inches out from the center of rotation of sleeve 23 when the radar device is -h'orizor'ital and it is zero inches outwhe'n theradar device is vertical. At all positions its movement is proportional to the cosine of the angle of elevation of the radar.

The azimuthfielsy'nAdrives Selsyn AA and drivs' -t ie gear 31 which in turn rotates'arm 28 and cair-i'e's around the route in an eccentric manner depending upon the lateral separation of support 22 from post 33. This lateral separation is determined by the elevation of the radar, 'a'ifectingSelsynCC torotate gear' l2.

or the "right plan position indicator, Selsyn orks one Selsyn'5l. The variable resistance 13 en 'segment lii controls 'the'g'ain of the sweep circuit for the right plan position indicator so that the sweep length is proportional to the cosine of the angle of elevation. In order to accomplish this, the resistance 13 must be tapered to match the cosine of the angle of elevation. That is, the resistance must be graduated by unit length and not have uniform resistance per unit length.

I claim:

1. In a stereoscopic device, a right plate and a left plate spaced apart, identical map designs positioned on said plates, a plurality of equally spaced concentric circles on said right plate, a plurality of corresponding eccentrically spaced circles on said left plate, corresponding circles having the same radius and having centers progressively displaced from the center of said map as the radius is reduced, a symmetrical system of lines on said right plate connecting the outer circle with the center, elements of said line system terminating symmetrically and consecutively on equally spaced circles intermediate between the outer circle and the center, a system of lines on said left plate similar to those on the right plate and connecting corresponding displaced circles whereby the circle and line systems when viewed in stereoscopic fusion appear as a series of conical ridges and valleys on whose side walls appear a series of contour lines intermediate between the ground plane and the apices of ridges.

2. In a device for indicating the position of an object in space above the ground plane, stereoscopic means comprising, a right and a left plate each provided with identical transparent map designs and supported for stereoscopic viewing, each map having inscribed thereon different but corresponding grid-like designs, said right grid design comprising a series of concentric equally spaced circles, and a symmetrical system of lines connecting the outer circle with the center, elements of said line system terminating symmetrically and consecutively on equally spaced circles intermediate between the outer circle and the center, said left grid design comprising a series of circles similar to those on the right plate, corresponding circles having the same radius and having their centers respectively displaced from the center of the outer circle as the radii are reduced, and a system of lines similar to those on the right plate connecting the outer circle with the center of the innermost circle, elements of said line system terminating on corresponding intermediate circles whereby the circle and line systems when viewed in stereoscopic fusion appear as a series of ridges and valleys on whose side walls appear a series of contour lines intermediate between the ground plane and the apices of said ridges.

RICHARD H. RANGER.

(References on following page) REFERENCES CITED The following references-are of record in the file of this patent:

Number Number Number 10 4,506

Name Date Lyman et a1 Jan. 7, 1941 Babcock et a1 Jan. 12, 1943 Bogopolsky June 27, 1944 Wood Oct. 3, 1944 MacNeille et a1 Nov. 13, 1945 FOREIGN PATENTS Country Date Great Britain 1910 OTHER REFERENCES Judge, Arthur W.: Stereoscopic Photography, published in 1926 by Chapman & Hall Ltd London, pages 18, 19, 134, 35, 172, 229, 230. 

